1. Field of the Invention
The present invention relates in general to a multiple fluid atomizer, and more particularly to an internal mix atomizer and a method for mixing fluids within the atomizer.
2. Description of the Related Art
Dual fluid atomization is a method which uses the momentum supplied by a compressible fluid (usually air or steam) to break up a second fluid (usually a liquid) into very fine droplets. In many applications it is necessary to mix a third fluid into the atomized liquid and surrounding fluid (usually a gas). For the case described here, this is done by internally mixing the liquid, the compressible fluid, and the third fluid, and spraying the mixture into the surroundings through small orifices in the nozzle of the atomizer. The momentum of the atomizer jets will provide rapid mixing of these three fluids and the surrounding gas in addition to breaking up the liquids. Such a technique may be applied to beneficially introduce mixtures into a chemical reactor or a boiler.
Typically, a tank equipped with an agitator has been used to mix a second fluid into a liquid. The agitator provides the energy needed for the initial mixing and thereafter operates to maintain the mixture. The mixed fluid is then transported from the tank to the reactor or boiler with the mixture being maintained during transport by using one or more in-line mixers. Keeping fluids mixed can be especially difficult in applications where the two fluids are immiscible or where a solid that has a tendency to settle out is mixed in. This method of mixing has certain economic and operational drawbacks. The agitator and in-line mixer(s) require a capital outlay for their purchase and installation and further expenditures for their operation and upkeep, including expenses for the energy needed to operate them. In addition, preparing the mixture in a tank limits the ability to change the mixture ratio in response to variations in reactor or boiler operating conditions. An additional concern arises in applications where there are competing side reactions in the two fluids if they are mixed for too long before entering the reactor.
Dual fluid atomizer designs are known which utilize a compressible fluid such as steam or air to atomize another fluid which may be a gas, a liquid, or a liquid which is laden with suspended solid particles (a slurry). (See U.S. Pat. No. 5,129,583 and U.S. Pat. No. 4,819,878.) Nothing in either of these two references suggests use of the compressible fluid to internally mix a second and a third fluid and to break up the resulting mixture into fine droplets. Other references of interest are Clyde Orr, Jr. Particulate Technology, Macmillan Company, New York, 1966; and W. L. McCabe and J. C. Smith, Unit Operations of Chemical Engineering, Third Edition, McGraw-Hill Book Company, New York, 1976.